This proposal outlines the salient features of the design and development of new synthetic methods and reagents and their application to the synthesis of cytotoxic sesquiterpenes, sesquiterpene synthons, and related potential cancer chemotherapeutic agents. The major thrust of this work will focus on the following objectives: (a) The development of new synthetic methods which formally allow for the metathesis and divinylation of olefins. (b) The application of the formal olefin metathesis (FOM) reaction to the synthesis of germacrane and elemane sesquiterpenes. (c) The application of the olefin divinylation (OD) method to the synthesis of iridoid terpenes, related alkaloids, and alpha-methylene-gamma-lactones. (d) The development of new organo-metallic reagents for the preparation of divinylcyclopropanes. (e) The application of the above reagents to ring annelation strategies and the synthesis of cytotoxic pseudoguaianes. (f) Studies on new synthetic strategies to the cytotoxic hydro-azulenes based on the divinylcyclopropane rearrangement. (g) The development of a new three-carbon dienophile and the study of this reagent in the synthesis of odd-membered carbocycles common to the cytotoxic hydroazulenes.